Michael Stephen Column

UK Parliamentary Committee and Bad News for Compostable Plastics (FREE)

Today Michael writes about the Environment Committee of the UK Parliament, and about some more bad news for plastic marketed as “compostable.” This is a FREE article

UK Parliamentary Committee

I have been reading the transcript of the hearing on Plastic Waste on 18th January 2022, when three scientists gave evidence to the Environment Select Committee of the UK Parliament. It leads me to believe that when parliaments and governments are considering oxo-biodegradable plastic it is unwise for them to rely on the advice of experts who are not experts in oxo-biodegradable technology. 

  • Oxo-biodegradable plastic

The following evidence relating to oxodegradable and/or oxo-biodegradable plastic attracted my attention:  “From a lifecycle perspective, what is interesting to me is not just whether they make microplastics but how long the degradation takes and what forms the plastics go through on the way there. It is well enough to say that, in X years, there will be nothing left and it will all have turned into carbon dioxide and water, but, if it takes X years to do that, what impact has that piece of plastic had if it is in the environment along the way?”

The answer to this is that there is no point in making a plastic article which will degrade instantly, as it would have no useful life, but if an oxo-biodegradable plastic item takes X years to turn into carbon dioxide and water, an ordinary plastic item would take X  multipled by 90. Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO2 Evolution and Quantification  (para. 2.3) 

This is why ordinary plastic should no longer be used for everyday plastic items, because it will be impacting on the environment for ninety times as long.

The witness continued “One of the challenges you have with the oxo-degradables is that they are almost billed as: if they end up in the environment, it does not matter.”  The witness has not appreciated the difference between oxo-degradables and oxo-biodegradables.  “Oxo-degradation” is defined by CEN (the European Standards authority) in TR15351 as “degradation identified as resulting from oxidative cleavage of macromolecules.”  This describes ordinary plastics, which abiotically degrade by oxidation in the open environment and create microplastics, but do not become biodegradable except over a very long period of time.  These are not “billed” as degradable at all.

By contrast, “oxo-biodegradation is defined by CEN as “degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively”.  This means that the plastic degrades by oxidation until its molecular weight is low enough to be accessible to bacteria and fungi, who then recycle it back into nature.  The statement that “they are almost billed as: if they end up in the environment, it does not matter” is not a scientific statement – and no advertisement is cited. 

I am not aware of any such advertisement.  The basis on which Oxo-biodegradable plastic is marketed is that it should be disposed of responsibly like all other consumer items, but we are all aware that this does not always happen.  What then is to be done about it?  Do we leave it to fall into microplastics and lie or float around in the environment for 100 years, or do we upgrade it with oxo-biodegradable technology so that it will last for a very much shorter time?   As one of the other witnesses said “We hope that things will not get out, but we have to be realistic that some stuff will.”

It is unlikely that the kind of person who throws litter out of a car window will care whether it is biodegradable or not, and in any event, much of the plastic which gets into the open environment escapes accidentally from the waste-management system without any conscious decision by anyone.  In any event, there is no need for an everyday oxo-biodegradable plastic item to be labelled as such, because it is not intended for long-term use; it can be used in the same way as ordinary plastic during its useful life; it can be landfilled or incinerated in the same way as ordinary plastic, and it can be recycled without separation if collected before it has degraded. Recycling Reports

According to another witness  “Oxo-degradable plastics, through the balance of evidence, have been shown to be harmful, because they produce microplastics and do not truly disappear in the environment. We have sufficient evidence to say that now.”

There is actually no sufficient evidence.  The witness seems unaware that the European Chemicals Agency were asked to study this subject in 2018, and they issued a Call for Evidence to which many stakeholders responded. They also read the reports published by the European Commission, and after ten months (30.10.18) they said that they were not convinced that microplastics were formed.  If the European Union’s own experts were not convinced we don’t see how this witness can be so adamant.

The witness continued “You mentioned oxo-biodegradable. There are other terms such as “triggered degradation plastics.”  I have never heard of this description before.   It is not a scientific definition, and serves only to cause confusion.  It is better to keep to the CEN definitions in TR15351 mentioned above.

“These are newer materials that claim to offer the benefits of additive-induced degradation without the harms of oxo-degradation. They follow a similar initial process, which is breakdown by heat or UV, but then they are often claimed to undergo further biodegradation in the environment and disappear more quickly.”  The witness seems to be referring to a material offered by a startup company and described as “biotransformation.”  However, if you look at their patent application you see that it is essentially an oxo-biodegradable plastic which, as defined by CEN  degrades by “oxidative and cell-mediated phenomena, either simultaneously or successively.”  This means, as mentioned above, that the plastic degrades by oxidation until its molecular weight is low enough to be accessible to bacteria and fungi, who then recycle it back into nature.  The process is not in fact dependant on heat or uv.

The witness continued “More impartial assessment is necessary to determine the impact of these newer types of plastics, and that includes, timescales and impact on the environment.”  The witness seems unaware of the report published in 2021 of the Oxomar research Oxomar Report    This is the most significant piece of actual scientific work (as distinct from literature reviews) conducted in recent years, but none of the witnesses even mentioned it. 

This was a three-year study, sponsored by the French government, which proves beyond doubt that oxo-biodegradable plastic does biodegrade in the marine environment.  To be quite sure, the scientists have also exposed a sample containing carbon 13 to bacteria, and they identified carbon 13 in the bacteria themselves – proving that the bacteria had bioassimilated the material. They are writing a further report on this.

As to timescale, none of the witnesses sems aware of the research at Queen Mary University London mentioned above, which has shown that the biodegradation can be up to ninety times faster than ordinary plastic. 

Microbial Degradation of Plastic in Aqueous Solutions Demonstrated by CO2 Evolution and Quantification  (para. 2.3) 

The witness continued “Some of these are claimed to be safe for recycling, and the impact on the waste management system is also really important to consider here. To prevent the unintended consequences that we see in the case of oxo-degradable plastics, more independent assessment is needed before we determine these to be useful or safe on the market.”

The response to this as follows: (a)The type of biodegradable plastic marketed as “compostable” will certainly contaminate an ordinary plastic recycling stream.  (b) Oxodegradable plastic will not contaminate an ordinary plastic recycling stream, as it is ordinary plastic itself.  (c) With regard to oxo-biodegradable plastic, this has been commercially available for more than 20 years and there have been no reports that it has caused any problems when recycled together with ordinary plastic.  The everyday plastic items for which oxo-biodegradable technology is used are not in any event worth recycling in economic or environmental terms, but expert studies in Austria and South Africa show that it can be safely recycled without separation if so desired.  Recycling Reports

Another witness said“Part of the reason why a lot of the common plastics that we use perform so well is that they are semi-crystalline. They have crystalline regions of really well-ordered chains.

….. They have these and they give strength to the material, and the amorphous regions that are very disordered give the ductility to the material. Those are the bits that will biodegrade or compost more quickly, and you are left with the little crystalline bits that go into microplastics and then degrade down to nanoplastics. They are the bits that are the most challenging environmental degradation to deal with.” That would require some really inventive chemistry to get around, but it is not impossible.

It is not impossible, and this issue has already been addressed by scientists familiar with oxo-biodegradable technology.  They have concluded that oxidation does occurnot only in the amorphous regions of the polypropylene but also in the chain portions which initially formed part of highly regular crystalline structures. See Arráez, F. J., Arnal, M. L., & Müller, A. J. (2018). Journal of Applied Polymer Science135(14). Thermal and UV degradation of polypropylene with pro-oxidant. Abiotic characterization  

With regard to Standards, I was really surprised that a witness said “As far as I am aware, at least, there is not a standard on environmental degradability to follow, where we could look at what their impact is and the timeline of that in the environment, should a plastic get out to waste.”   In fact, since 2004 we have had the American standard ASTM D6954 for “Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation” See the evidence about this Standard given to the UK government by one of its authors, Dr. Graham Swift https://www.biodeg.org/wp-content/uploads/2021/02/Swift-evidence-to-BEIS.pdf  There are similar standards in the UK, France, Sweden, the UAE, Saudi Arabia and other countries.

With regard to ordinary plastics, I agree with the witness who said “They have been preferred and designed around for 50 years. Let us be honest: they have really great properties for what we want them for. We like to use them because they are convenient, lightweight, strong and ductile—all of the things that we want to use them for—and they are cheap. Ethylene is not far off a waste product from the oil industry that they can then make into plastic. The scalability question has also been dealt with. These are made in millions of tonnes a year. In my lab, going from a 10 gram scale to even a 10 litre or 10 kilogram scale is a really difficult thing to do, never mind up into the tonnes.

There are a lot more pros for current plastics. As for the cons of them and where biodegradable plastics really have the advantage, I have written down “environmental legacy.” That is the con or the downside of plastics, and it is not intended. I do not think anyone set out to litter the world with plastics. There was a report just this morning on the news of how far and wide plastics are and how long it is going to take us, if ever, to have a world that they are not polluting from what we have done already. There is a recent study that showed that there is more to come, and there is an awful lot more in our land and rivers than are out there in the oceans at the moment.

The reference to where biodegradable plastics really have the advantage, is to oxo-biodegradable plastics, which are designed to biodegrade if they get into the open environment.  It is not a reference to bio-based plastics, which either do not biodegrade at all or to those marketed as compostable, which need to be collected and taken to an industrial composting facility.

As the witness said “the cost of continuing with the present is a very expensive future in terms of pollution” and that is why all everyday plastic needs to be upgraded with oxo-biodegradable technology.  In the UK, there has already been too much delay, caused by faulty advice and muddled thinking at DEFRA, and as a result many thousands of tonnes of ordinary plastic have escaped into the open environment.  They will still be there in 50 years time, and DEFRA are to blame for that.

  • Bio-based plastic

There are bio-based plastics marketed as compostable, but this is deceptive advertising because they do not convert into compost.  The relevant Standard (EN13432) requires them to convert rapidly into CO2 – not into compost, and they do not therefore provide any plant nutrition.  It is also deceptive to describe them as biodegradable, because they are designed to biodegrade in the special conditions found in an industrial composting facility – not in the open environment.

The Chairman asked “if you are using compost that has a biodegradable plastic in it, we are really conscious of whether this is going to break completely down and be taken up by the plant as a nutrient, or whether it is just going to stay in the soil as a small particle. The jury is still out, is it not, on a lot of these compostable plastics? What is your view on it?   As to these plastics generally  see Compostable Plastics 

I would agree with the witness who replied “My view is that the European standard [EN13432] does not go far enough in terms of what the plastic has to break down to under the conditions at a given time. They are quite forcing conditions for a degradation. You are talking about 55 degrees centigrade, with added microbes, which you are not going to find on the average field in the UK.

It does not get that warm.  If you get these plastics that are not fully degraded—and there will be

these little nanoplastic crystalline regions—and you put them on your field, they are not going to continue to degrade at an appreciable rate. You are still left with them and you are introducing these nanoplastics into the environment.”

I would agree, and for this reason, bio-based plastics marketed as “compostable” should not be used for agricultural mulch film.  However, successful trials have been done in real-world conditions in Wales with oxo-biodegradable mulch film, which is designed to biodegrade in the conditions normally found in a field.  See Pembroke Mulching Film Trial

A Member of the Committee said “the Government’s innovation strategy last year said that biobased plastics would play a significant role in the economy by 2035. “Where fossil-derived … plastics are required, biomanufacturing will deliver biobased and waste derived alternatives in 80% of the cases”; that is what they said. What the Committee takes from what you have said today is that we do not really know and we do not have enough information about the full lifecycle of these, how they break down in the soil and what the impact may be.”

The witness replied “You can make polythene from biobased resources. It is still the same material and will still persist in the environment for the same amount of time as oil-based polythene, with all the challenges that [another witness] pointed out in terms of energy intensity. Also, the chemistry of having to do that may involve some other, not particularly pleasant chemical processes that we may want to avoid, if we can.”

I would agree with this witness who said “There should be a very clear distinction between “biosourced” and “biodegradable” or “compostable” ….because those are completely different things that are often confused. As soon as you put the word “bio” in there, you jump to thinking that they are the same thing, and they are absolutely not.  You can make polythene from sugarcane. The distinction needs to be made. [Another witness] raised the point that it is probably no better than making it from fossil, other than you are not digging up the fossil from the ground, but that is probably going to get dug up anyway, for other reasons.”  Exactly right – oil is primarily extracted from the ground to make fuels and lubricants, and would be extracted even if plastics did not exist.

The witness continued: If you take a PET bottle like you buy soft drinks in, you can make that from fossil sources or from biobased sources. There are two main ingredients in it and you can make both of them from either fossil or bio sources.  With one of those ingredients, if you switch to biobased sources, you will have a lower carbon footprint than the fossil equivalent, which is why a lot of bottles are 30% made from plants. However, the carbon footprint of making the other 70%, from bio sources is huge compared to using fossil sources. In that example, we should not be incentivising switching that second ingredient, if carbon is the thing that we care about. If what we care about is the bottle and whether it will end up as waste, it does not really matter which source it came from in the first place.”

  • Reusable bags

One of the witnesses said “People buy bags for life but we have been working with a supermarket, which, when it interviewed people at the checkout, found that 44% of people had left their bags at home so were not reusing them; 44% had left them in the car, so were not reusing them; only 10% of people had their reusable bag with them at the checkout.”

The problem with reusable bags is that they contain a lot more plastic than the traditional lightweight checkout bag.  Even re-usable bags get discarded at the end of their useful life, and they need to be made with oxo-biodegradable technology so that they will not lie or float around for decades. The useful life can be programmed as desired by adjusting the formulation of the masterbatch, and they can be recycled if collected before the end of their useful life.

More Bad News for Plastic Marketed as Compostable

In addition to the comments made above in the Environment Committee, an article in the Daily Telegraph on 30th March reported that the UK Government has said compostable packaging should be thrown into the bin because there is little evidence it is good for compost and it can contaminate recycling.  “Do not recycle” labels must be added to all such packaging under new rules to be introduced by the Government.

The new rules signal a policy change, as the Government had recently said all packaging should be ‘recyclable, reusable or compostable’ by 2025 “Even when properly broken down in industrial composting facilities, there is insufficient evidence that compostable packaging provides “ecological or agricultural benefits to soils or digestate” the Government has said.

Compostable coffee machine pods, takeaway containers and delivery packaging have grown in popularity in recent years, as companies respond to consumer concerns over the impact of single use plastics, but experts warn of greenwashing.  Compostable packaging is designed to break down in specific circumstances and most do not break down in home composting facilities. They can be broken down in industrial facilities via food and garden waste, but not all councils have access, and there is little evidence that the plastics add nutrients to the final products.

Around half of local councils send their green waste to anaerobic digestion, where it is processed and turned into biogas and fertiliser, but it cannot process the plastic. Compostable packaging materials are not widely targeted, collected or processed as part of normal council waste services in the UK because many of these types of packaging don’t perform as advertised when treated in real-world conditions at industrial composting facilities.   In many cases, packaging and other objects are screened out before household garden and food waste is sent for composting anyway, and are treated as general rubbish.  See also Compostable Plastics 

Michael Stephen

Michael Stephen is a lawyer and was a member of the United Kingdom Parliament, where he served on the Environment Select Committee. When he left Parliament Symphony Environmental Technologies Plc. attracted his attention because of his interest in the environment. He is now Deputy Chairman of Symphony, which is listed on the AIM market of the London Stock Exchange, and is the founder and Chairman of the Oxo-biodegradable Plastics Association.

Earlier Postings in this Column

All articles of Michael Stephen can be found here

Interview with Michael Stephen


The opinions expressed here by Michael Stephen and other columnists are their own, not those of Bioplasticsnews.com.

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